In 2004, Macquarie Centre for Cognitive Science and the philosophy department at Macquarie University (Sydney) organized a conference on "Delusion, Self-Deception and Affective Influences on Belief Formation", in which many of the papers of this volume were first presented. As the editors warn in their introduction, their aim was to foster empirical and conceptual connections between current research on delusion and self-deception. For this, they brought together a group of scholars in various disciplines, most of them with a remarkable competence for interdisciplinary discussion. The connecting thread in their analyses features in the title of the book: the role played by affects and emotions in the formation of delusional or self-deceptive beliefs. However, the unity of this compilation lies mostly in the extraordinary editorial work of Tim Bayne and Jordi Fernández, who have not only provided thorough author and subject indexes, but also encouraged cross-references between papers and wrote an introduction intended as a map for the terrain explored thereafter.

In my view, this volume hinges on five papers on two delusions: the Capgras delusion (the belief that a familiar person has been replaced by an impostor) and anosognosia for hemiplegia (the delusional belief of being able to move your paralyzed limbs). These five papers present the standard theories of delusion, with special emphasis on the role of emotions in the explanation of the two cases in point, but with very few mentions of its connections to self-deception. Three additional papers bridge this gap, exploring possible connection between the explanation of these delusions and Mele's theory of self-deception. Three more papers discuss the role of emotion in belief formation with no explicit link with any of the theories above. Following this division, I will provide a quick overview giving just a glimpse of the topics discussed. The reader is warned that the book is incredibly rich in ideas and evidence on every topic discussed and I am afraid many will be missing here.

The most successful empirical approach (so far) to explain the Capgras delusion focuses on the cognitive mechanisms of face recognition drawing on research on prosopagnosia. The Capgras delusion would arise when the subject is somehow able to recognize a familiar face but without experiencing the usual emotional response to it (as measured by skin conductance response). The damaged mechanisms in the brain explaining this diverging response are still under discussion, as Philip Gerrans informs us in ch. 7. There are different approaches to modeling the belief distortion in this delusion, namely two: endorsement models and explanationist models. In the former, the patient believes in the content of her experience, where the delusion lies. In the latter, the delusion is an attempt to explain an usual experience (e.g., the lack of emotional response). Gerrans develops an endorsement account focused on a purely cognitive misidentification (failure to acknowledge the numerical identity between the familiar face and the person the patient knows). Elisabeth Pacherie (ch. 6) considers alternative accounts of the Capgras delusion, pondering to what extent they support the endorsement approach. She is inclined to think that the delusion arises from the inability to process dynamic information about the emotions expressed by familiar faces. Pacherie furthers this approach with an argument for the modularity of the feelings of familiarity. If the delusion lies in the perceived experience, it is important to demarcate it from belief and Fodor claims that modularity is one such demarcation criterion. An additional argument against the explanationists provided by Pacherie is that, even if the subject forms a delusional belief, she applies correctly the usual checking procedures (further observation, background knowledge, testimony) but they fail to yield disconfirming evidence.

A second division in the approaches to delusion can be made between one and two-factor approaches. The former invoke a perceptual and/or affective deficit that generates the belief and the latter add a second deficit to explain why such belief is not rejected. Brian McLaughlin (ch. 8) takes issue with the standard one-deficit account of Brian Maher, according to whom delusional beliefs "function to explain anomalous experiences resulting from neuropsychological anomalies" and this would be a rational response. In the Capgras delusion, argues McLaughlin, this would not be the case by any standard of epistemic justification, since the delusional belief coheres badly with our background knowledge. McLaughlin proposes a model for the Capgras delusion in which two types of beliefs would be acquired by separate routes: a linchpin belief (about the unfamiliarity of the face) and a thematic belief (about the impersonation). It is epistemically irrational on the part of the patient not to reject this second belief, arrived at by paranoid-driven reasoning. McLauglin develops the concept of existential feelings, among which familiarity would feature. Given the characteristics of these feelings, McLaughlin is skeptical about our natural ability to override them. So much for the Capgras delusion

Anne Aimola Davies and co-authors (ch. 10) analyze anosognosia for hemiplegia in the two-factor framework for delusions presenting a broad review of the available empirical evidence (including their own data) about the role played by motivational and cognitive factors. The first factor would be here "an impairment that prevents the patient's paralysis or weakness from making itself known to the patient through immediate experience of motor failure". The second factor, in turn, would be "an impairment that prevents the patient from making appropriate use of other available evidence of his or her motor impairments". The authors present their own conjectures about the functional nature ("an impairment of working memory or executive process") and neural basis ("the right frontal region of the brain") of this second factor. Frédérique de Vignemont (ch. 12) systematically compares hysterical paralysis and anosognosia, the former apparently being the mirror image of the latter: patients feel paralyzed although they are physically able to move. De Vignemont points out that hysterical paralysis is grounded in delusional beliefs about the extent and source of their inability to move. It is a local paralysis and does not arise from organic damage. However, the experience of being paralyzed generates the delusion as a normal response. Their anxiety at the paralysis keeps them frozen: this explains their inability to reject the original delusion without the intervention of a second factor. They are indeed paralysed.

So much for the study of delusions. As for its connection with self-deception, Alfred Mele (ch. 3) presents a brief summary of his own deflationary theory of this latter and an analysis of a few delusions in this perspective. Since Mele's account of self-deception hinges on the influence of motivational factors in lay hypothesis testing and such factors do not necessarily feature in the explanation of, e.g., the Capgras delusion, he concludes (tentatively) that deluded subjects may not be deceiving themselves. Martin Davies (ch. 4) makes the more significant effort in the volume to bring together the analysis of deception and self-delusion. After a brief review of the standard one- and two-factor accounts of this latter and a summary of Mele's theory on the former, Davies discusses how motivational biases can feature in either factor or in the route from experience to belief. When they affect the second factor, Davies concludes that we have the clearest cases of an overlap of delusion with Mele's self-deception. Neil Levy (ch. 11) argues, against Mele, that there is one real case of self-deception in which the subject believes a proposition and its negation. This would be anosognosia for hemiplegia, where subjects –in a certain sense that Levy specifies– simultaneously believe that their limb is healthy and significantly impaired

The remaining three chapters are somehow at odds with the theoretical approaches presented so far. In chapter 1, Peter Ditto provides a brief overview of fifty years of psychological research on motivated cognition, which serves as an introduction to his own contribution, the quantity of processing view. According to this view, we would we react more skeptically and invest more time and resources in the cognitive processing of those pieces of information inconsistent with our preferences. As the editors notice in their introduction, this view does not seem to encompass delusions, where it often happens that the subject cannot reject a delusional belief despite its negative affects. Drawing on recent research in cognitive neuroscience (namely, appraisal theory and the somatic marker hypothesis), Michael Spezio and Ralph Adolphs (ch. 5) substantiate the claim that emotions mediate in the processing of information in the brain. As an illustration, they briefly show how emotional processing underlies our moral judgments. The editors observe here that it is an open question whether this account may apply to belief formation in general. In the final chapter of the book, Andy Egan proceeds to a philosophical discussion of the status of delusions and self-deception as mental states. Invoking a functional role conception of mental states, Egan argues that delusions are intermediate states between belief and imagination whereas self-deception is an intermediate state between belief and desire. As the editors point out, this is at variance with the assumption that now orientates empirical research on both phenomena: they are just beliefs.

Despite the effort of the editors, this volume is often difficult to read. The different theories and empirical findings about the two delusions analysed are presented time and again throughout the eight core papers. However, were it not for Davies' paper, I guess I would be lost as to the connection between the two phenomena. Or more precisely between the standard theories of delusion and Mele's theory of self-deception: no alternative approach is discussed in the book. This volume features in a series that "provides readers with a summary of the current state-of-the-art in a field". The disunity in the two fields of study covered in this volume is adequately captured in the papers compiled.

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